Semiconductor power loss protecting method - waiting set time between disconnection of one of 2 anti-parallel bridge circuits in converter and switching in other bridge circuit.

摘要

The protection method for semiconductor switches (1--V1) in a DC/AC converter feeding energy back into the supply network (U,V,W), involves using a waiting time introduced between the disconnection of one of 2 anti-parallel bridge circuits (1,8) incorporated in the converter and switching in of the other bridge circuit. When the network voltage fails a common control pulse is provided for the semiconductor switches causing them to be conductive when no working time is present. Pref. the anti-parallel bridge circuits are coupled to an intermediate circuit with a capacitor (3) in parallel with a free-running diode (4), across which a constant DC voltage (Ud=const) is obtained, each bridge circuit using 3-phase AC network. ADVANTAGE - Allows immediate operation of DC-AC converter when normal voltage is restored.